Re: [boost] [rfc] Preliminary Hash Library

Subject: Re: [boost] [rfc] Preliminary Hash Library
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2010-05-06 02:51:12

_____________________
Vicente Juan Botet Escribá
http://viboes.blogspot.com/

----- Original Message ----- 
From: "Scott McMurray" <me22.ca+boost_at_[hidden]>
To: "Boost Developers List" <boost_at_[hidden]>
Sent: Thursday, May 06, 2010 2:55 AM
Subject: [boost] [rfc] Preliminary Hash Library

> 
> I've boostified, cleaned up, and documented the Hash Library I
> mentioned here about a month ago.  Comments, complaints, suggestions,
> and questions appreciated.
> 
> Source code is in the sandbox at http://svn.boost.org/svn/boost/sandbox/hash/
> 
> Documentation can be read online at http://www.cs.mcgill.ca/~smcmur/hash/
> 
> I was very pleased by how the implementation came together, as
> templates mean that all the hash algorithms share a substantial
> portion of their code.
> 
> Those details are all hidden from the user, though.  Here's an example
> showing the simplest use of the library:
> 
> #include <boost/hash.hpp>
> 
> #include <iostream>
> #include <string>
> 
> int main() {
>    std::string s = "Hello World!";
>    typedef boost::hash::sha2<256> HashPolicy;
>    HashPolicy::digest_type digest = boost::hash::compute_digest<HashPolicy>(s);
>    std::cout << digest << "\n";
> }
> 
> Thanks,
> ~ Scott McMurray
> _______________________________________________
> Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
>

Hi,

thanks for sharing this library.

After reading some pages, I have two question:
* Where is documented the  MessageDigest concept ?
* How compare the optimized and not optimized code (efficiency) showed in the examples?

#ifdef BOOST_HASH_NO_OPTIMIZATION
    return boost::hash::compute_digest<hash_policy>(
               std::istreambuf_iterator<char>(sbuf),
               std::istreambuf_iterator<char>()
           );
#else
    hash_policy::stream_hash<8>::type hash;
    for (;;) {
        boost::array<char, 8*1024> buf;
        std::streamsize n = sbuf->sgetn(&buf[0], buf.size());
        if (!n) break;
        hash.update_n(buf.begin(), n);
    }
    return hash.end_message();
#endif          

It would be possible to define a template function that provides the optimized code?

Best,
Vicente